There are many different types of known washer-scrubbers. These include plate column scrubbers, stationary packing scrubbers, moving bed scrubbers, fibrous packing scrubbers, preformed spray scrubbers, etc. The use of baffles and sprays has been disclosed in a number of patents. U.S. Pat. No. 1,169,764 issued to Brassert discloses a method of gas washing which uses a baffle plate having an array of circular holes radially arranged in circles of increasing diameter and four spray heads around the periphery of the baffle plate at 90 degrees to each other. U.S. Pat. No. 1,467,184 issued to Mathesius discloses the use of 3 sets of baffles with two baffle plates in each set. Each baffle plate consists of four grills with each grill having upwardly inclined sides inclined oppositely to the grills immediately above and/or below. The spray heads are heads are mounted on the wall of the tower below each set of baffles and are directed from the sides of the tower towards the center and upwardly at an average angle of about 45 degrees with the horizontal at the lowest baffle in each set.
U.S. Pat. No. 3,765,659 issued to Reilly discloses a series of horizontally disposed, vertically spaced apart pairs of baffle plates with the holes of one plate of the pair underlying solid areas of the next higher plate. The hole diameters decrease and the number increase from one pair to the next higher pair so that the total area of the holes remains the same. The spray heads are mounted heads directed vertically beneath each pair of plates. The spray pattern, in combination with the hole size and positioning, determine the efficiency of scrubbing an exhaust gas. If one sprays with droplets that are too large then the efficiency of scrubbing is reduced dramatically. Most existing systems spray with droplets of 400 microns and larger. If the holes are too small then there is a risk of blockage by particles and sludge. If they are too large then more particulate is lost and the scrubbing efficiency is reduced.
Another important factor in the design of a scrubber is cost. For example, Reilly discloses the use of pairs of baffle plates with spray applied only to the bottom plate. The top plate of each pair has no spray applied to it and, thus, would tend to clog up with sludge. Moreover, the sprinkler arrangement is affixed to the walls of the tower heads and is expensive and not easily installed or serviced. Finally, Reilly and the other above-mentioned patents all appear to employ spray nozzles that produce droplets of 400 microns or larger and so are not capable of efficient trapping of the particulates. Many conventional systems attempt to compensate for the large spray size by flooding the scrubbing chamber with fog or spray in order to trap more of the particulate. However, excessive fog or spray merely produces water droplets which again dramatically reduce the collection efficiency.
Accordingly, it is an object of the invention to provide an improved scrubber.